8 Best Polyurethane Finishes for Wood

Buying Polyurethane

Unlike lacquer, shellac and varnish, which have been around for centuries, polyurethane is a product of 20th-century lab technology.

In some ways, polyurethane is better than traditional film coating. It’s a curing finish instead of a drying finish, like lacquer. The process is irreversible, so the best polyurethane finish has excellent chemical and moisture resistance.

Polyurethane comes in solvent and water-based formulations. Both are easy to apply. Water-based formulations dry more quickly, release fewer volatile organic compounds (VOCs) and make cleanup easier, so they’re more popular.

That doesn’t mean you should always opt for a water-based product, however. Solvent-based formulations have characteristics that water-based products can’t duplicate. Nor is polyurethane always a suitable substitute for lacquer or shellac, which can be layered and buffed to give an ultra-smooth protective coating with a more natural appearance.

A polyurethane finish is suitable for all but the highest quality interior furniture and woodwork, and it’s probably the No. 1 clear finish for exterior woodwork. Modern exterior formulations closely resemble traditional varnishes that include sun-blocking resins to protect wood from UV deterioration.

Choosing the best polyurethane for a particular project involves the following considerations:

• Use: Indoors, it’s good on furniture, woodwork and wood floors, or as a protective coating over a layer of paint. Outdoors, you’ll find it on woodwork, furniture, decks and railings.
• Water- or solvent-based: Water-based finishes tend to have a more plastic-like appearance. Solvent-based products have more time to flow out before drying, creating a smoother finish. Solvent-based products tend to turn slightly amber after application, but water-based products don’t.
• Drying time: Water-based products tend to dry to the touch faster than solvent-based products, so you can apply more coats in a day. Curing time runs three to five days for most products.
• Sheen: Water- and solvent-based products come in a variety of sheens, including gloss, semi-gloss, satin and matte. Gloss finishes are more reflective, hence more noticeable. They’re also a little harder.
• Wipe-on, brush-on or spray-on: Wipe-on polyurethane products go on contoured surfaces (think turned chair legs), while brush-on polyurethane is generally for flat surfaces. Spray-on products work for both and guarantee stroke-free finishes, but are usually more expensive.
• Interior or exterior: Never use an indoor product outdoors. It lacks the extra sun-blocking solids, wears off in a year or two and does little to protect the wood.

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